Title: Microbial Ecology Part II. Speaker: Amit Dhingra Created by: (remove if same as speaker) online.wsu.edu

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1 Title: Microbial Ecology Part II Title: Instructor: What is Consetta the title Helmick of this lecture? Speaker: Amit Dhingra Created by: (remove if same as speaker) online.wsu.edu

2 Microbial Ecology Part II Microbial Ecology Sewage Treatment Water Treatment Solid waste Landfills Back yard composting Bioremediation

3 A Glimpse of History Long history of delivering water, removing wastes Ruins of Roman aqueducts seen in much of Europe Early sewers mostly large, open cesspools People recognized link between water, diseases long before discovery of microbial world In 330 B.C., Alexander the Great had armies boil water Sand filtration used in London, elsewhere in early 1800s In 1840s, Edwin Chadwick championed idea of waste removal via system of ceramic pipes flushed with water In 1848, Board of Health in England began installing similar sewage system in response to fears of cholera New York City did the same in 1866 By end of nineteenth century, water and sanitation systems in most large European, U.S. cities; cholera virtually disappeared in industrialized nations

4 Microorganisms in Treatment Microorganisms ultimate recyclers Play essential role in decomposition of our wastes Pathogens must be eliminated from sewage, water Potable water is safe for human consumption Recreational waters monitored for harmful pathogens Treatment of water, waste, polluted habitats a challenge Average American uses 150 gallons of water, generates 120 gallons of wastewater and 5 pounds of trash daily City of 1 million generates ~44 billion gallons of wastewater, ~1 million tons of trash annually

5 Wastewater Treatment Wastewater (sewage) composed of all materials of household plumbing system Municipal wastewater includes business, industrial waste In many cities, storm water runoff also included Most obvious reason to treat is removal of pathogens Prevent spread of disease via water of rivers, lakes Shellfish are filter feeders, concentrate microbes High nutrient content in sewage is also damaging Addition of nutrients to water leads to rapid growth of microbes; aerobes consume and deplete O 2 Fish, other aquatic animals die for lack of O 2 Effective wastewater treatment must decrease level of organic compounds, eliminate pathogens, pollutants

6 Municipal Wastewater Treatment Methods 1972 Federal Water Pollution Control Act (Clean Water Act) mandates primary and secondary treatment Following treatment, effluent (liquid portion) discharged Sludge (solid portion) additionally treated Primary Treatment Physical process to remove materials that will settle out Removes ~50% of solids and ~25% of BOD Raw sewage is screened to remove large objects Skimmers remove scum, other floating material Sewage sits in sedimentation tank; solids settle out Sludge is then removed Wastewater is sent for secondary treatment

7 Municipal Wastewater Treatment Methods (cont ) Secondary Treatment Chiefly biological process that converts suspended solids to inorganic compounds and cell mass for removal Eliminates as much as 95% of BOD Microbial growth actively encouraged Aerobes oxidize organic material to CO 2, H 2 O Microbial populations could be killed if too much toxic industrial waste or household materials added Methods used include: Activated sludge process Trickling filter (TF) system Lagoons Constructed wetlands

8 Municipal Wastewater Treatment Methods (cont ) Activated sludge process Mixed populations of aerobes grow as flocs (biofilms) Large numbers added by introducing small portion of leftover sludge from previous load Abundance of O 2 added by mixing wastewater in aerator Organic matter is converted to biomass, waste products Wastewater sent to sedimentation tank; flocs settle Sludge is removed Complication is bulking, caused by filamentous bacteria (e.g., Thiothrix) that overgrow, create buoyant mass

9 Municipal Wastewater Treatment Methods (cont ) Trickling filter (TF) system Frequently used in smaller wastewater treatment plants Rotating arm spreads effluent over bed of plastic pieces or course gravel and rocks Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Surfaces coated with biofilm (bacteria, fungi, algae, protozoa, nematodes) that degrades passing organic material Rate of flow adjusted for maximum degradation 1 2 Rotating arm distributes effluent Inlet pipe Effluent from primary treatment enters Filter media Biofilm-coated plastic pieces or coarse gravel and rocks Effluent trickles through. Outlet pipe Effluent from the filter goes to a sedimentation tank before advanced treatment or disinfection.

10 Municipal Wastewater Treatment Methods (cont ) Lagoons Wastewater remains in shallow ponds (days to weeks) Algae, cyanobacteria grow at surface, provide O 2 that allows aerobic organisms to degrade organic materials Constructed Wetlands Same principle, but designed as suitable wildlife habitat Effluent inlet Aquatic plants Effluent outlet Gradual slope to outlet Soil or gravel Watertight membrane (a) (b) Gary Crabbe/Alamy

11 Municipal Wastewater Treatment Methods (cont ) Advanced Treatment Any purification beyond secondary treatment May involve physical, chemical, or biological processes Usually expensive and thus uncommon historically Often designed to remove ammonia, nitrates, phosphates Compounds that foster growth of algae, cyanobacteria; accumulations create surface scum, increase BOD Ammonia removed by ammonia stripping Nitrates removed by denitrifying bacteria Anammox bacteria use ammonia for energy and nitrite as a terminal electron acceptor Phosphates eliminated via chemical precipitation

12 Municipal Wastewater Treatment Methods (cont ) Disinfection Chlorine, ozone, or UV light used to decrease numbers of microorganisms and viruses Water can be dechlorinated to avoid excessive release Anaerobic Digestion Sludge from sedimentation steps is digested anaerobically Various microbes act sequentially Organic compounds organic acids, CO 2, H 2 Organic acids acetate, CO 2, H 2 Acetate, CO 2, H 2 methane (CH 4 ) Water is removed, yields nutrient-rich stabilized sludge Can be incinerated, landfilled, or used to improve soils Some concerns about heavy metals, other pollutants

13 Primary Treatment Physical removal Secondary Treatment Activated sludge process Trickling filter system Lagoons Constructed wetlands Advanced Treatment Optional Raw sewage Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Primary Treatment physical removal of organic material Option 1 Option 2 Option 3 Option 4 Screens Effluent Sedimentation tank Sludge Secondary Treatment microbial degradation of organic material Activated sludge process Air or O 2 Aeration tank Sedimentation tank Trickling filter system Trickling filter Lagoons Constructed wetlands Sedimentation tank To sludge digestion To sludge digestion Anaerobic Sludge Digestion anaerobic microbial degradation of organic material Anaerobic digester Option B Option A Drying bed Advanced Treatment additional purifying treatments (chemical, physical, or microbial) Disposal, incineration, or use as a soil enhancer Treatments vary, but may include precipitation of phosphates, removal of ammonia, and biological degradation of nitrates. Disinfection destruction of pathogens and other microbes Treatments such as chlorination, UV light, ozone Discharge to receiving water

14 Individual Wastewater Treatment Systems Rural dwellings rely on septic systems for treatment Solid material settles, is degraded anaerobically in tank Effluent, with high BOD, percolates through drain field Aerobic microbes oxidize organic material Systems must be properly designed, monitored Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Wastewater from house Inspection access Access for cleaning Inspection access Scum Outlet to drain field Effluent (b) Sludge Household wastewater Septic tank Distribution box Drain field Gravel Vent pipe Perforated pipe (a)

15 Drinking Water Treatment and Testing Large cities typically obtain from surface waters Lakes and rivers, which may receive wastewater Also affected by characteristics of watershed Smaller communities often use groundwater Pumped from a well from an aquifer Layers of rock, sand, gravel containing water Somewhat protected, but still at risk of contamination Safe Drinking Water Act of 1974 regulates in U.S. Amended in 1986 and 1996; gives EPA authority EPA sets standards to control contaminants, may change in response to new concerns (e.g., Cryptosporidium oocysts, Giardia cysts, enteric viruses in drinking water)

16 Drinking Water Treatment and Testing Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Rainfall Soil Wastes Sludge Fertilizer Irrigation Septic tank Drinking water well Sewer line Defective well lining Groundwater

17 Water Treatment Processes Designed to eliminate pathogenic microbes, chemicals Water flows into reservoirs, particulate matter settles Water transferred to tank, mixed with chemical that causes suspended material to coagulate (flocculate) Mixture then flows to sedimentation tank; flocculate sinks Some microbes, other materials trapped Water is filtered to remove microbes including bacteria, protozoan cysts, oocysts Often thick bed of sand and gravel Organic chemicals removed by activated charcoal filtration Biofilms on filters use carbon from passing water, lowers content, results in less microbial growth in delivery pipes

18 Water Treatment Processes (continued ) Finally, water treated with chlorine or other disinfectants Kill any harmful viruses, bacteria, protozoa Disinfection by-products of chlorine may be carcinogenic UV, ozone increasingly used as alternatives Small amount of chlorine still added to prevent contamination Organic compounds consume free chlorine; more needed in waters with high concentrations Flocculation tank Disinfectant added Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Raw water reservoir Coagulant added Filtration unit Reservoir 4 Sedimentation tank Settling Large materials settle out. Coagulation Alum and other added chemicals combine with suspended material to form clumps. Sedimentation The coagulated materials settle to the bottom. Filtration Sand and gravel filters remove microorganisms including protozoan cysts and oocysts. Activated charcoal filters removed dissolved chemicals Disinfection and Storage Chlorine, ozone, or other chemical disinfectants are added. UV irradiation may also be used to destroy microbes. Consumer use

19 Water Testing Primary concern is possibility of contamination with any of a wide range of intestinal pathogens Not feasible to test all, so indicator organisms tested for Microbes routinely found in feces, survive longer than intestinal pathogens, and are easy to detect Total coliforms commonly used in U.S. as indicator Members of family Enterobacteriaceae Defined as facultatively anaerobic, Gram-negative, rod-shaped, non-spore-forming bacteria that ferment lactose, forming acid and gas within 48 hours at 35 C Fecal coliforms more likely to be of intestinal origin E. coli is most common

20 Microbiology of Solid Waste Sanitary Landfills for Solid Waste Disposal Widely used for non-hazardous waste disposal Minimize damage to human health, environment Previously, solid wastes often piled up in open-burning dumps that attracted insects and rodents Sanitary landfills must be located away from wetlands, earthquake-prone faults, flood plains, other sensitive areas Excavated site is lined with plastic sheets or special membrane on top of thick layer of clay Layer of sand with drainage pipes placed on top of this Wastes are added, compacted, and covered with soil Once full, landfill is covered with soil and plants Can be used for recreation, ultimately construction site Methane, gases vented; methane burned or recovered

21 Sanitary Landfills for Solid Waste Disposal (cont ) Several disadvantages Sites near urban, suburban areas are limited Methane gas must be removed as organic waste anaerobically decomposes; can take more than 50 years If buildings are constructed before methane is removed, disastrous gas explosions can occur Pollutants (e.g., heavy metals, pesticides) can leak into underground aquifers Very difficult to purify once contaminated Sanitary landfills traditionally low-cost; increased cost and decreased land availability is driving interest in alternatives Some cities charge based on size of container collected Recycling programs are being implemented with success

22 Municipal and Backyard Composting Alternative to landfills Composting is natural decomposition of organic material Increasingly used to reduce amount sent to landfills Some cities collect yard wastes separately from garbage Composted using machinery to make process more efficient Black organic material generated is commercially valuable, can be used to improve soils

23 Municipal and Backyard Composting (continued ) Backyard composting Leaves, grass, kitchen wastes Meats, fats not recommended Attract rodents, other pests Often, some soil and water added Inside of pile heats up due to microbial metabolism At C, pathogens are killed Thermophilic organisms remain If frequently aerated and kept moist, composting can take as little as 6 weeks Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (b) (a) a: Wave Royalty Free/Alamy; b: Sharon Dominick/iStock Exclusive/Getty Images

24 Microbiology of Bioremediation Bioremediation is use of microorganisms to degrade or detoxify pollutants in environment Usually takes advantage of organisms already present In some cases specific organisms are added Pollutants Most natural organic compounds are biodegradable Synthetic compounds more likely biodegradable if chemical composition is similar to that of natural ones Xenobiotics (synthetic compounds quite different from any in nature) more likely to persist Microbes unlikely to have suitable enzymes to degrade

25 Relative herbicide concentration Bioremediation (continued ) Pollutants Relatively slight molecular changes alter biodegradability Herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) well studied When 2,4-D is applied to soil, it is degraded by microbes within period of several weeks 2,4,5-T persists in soils for more than a year; a single chlorine is only difference Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display H 6 5 2,4-D H O C C O 1 4 Cl 10 Time (days) 2 Cl 3 OH 20 H 6 5 Cl 2,4,5-T H O C C O 1 4 Cl 2 Cl 3 25 OH

26 Bioremediation (continued ) Means of Bioremediation Many factors influence degradation rate of pollutants Providing adequate nutrients, ph near neutrality, raising temperature, optimal moisture all likely promote growth of microorganisms, increase degradation rate Biostimulation enhances local microbes by providing additional nutrients Petroleum-degrading microbes naturally present in seawater; limited by lack of nutrients Fertilizer containing nutrients increases degradation at least threefold